A double-blind, placebo-controlled, multi-center, crossover study to investigate the safety of the glucagon receptor antagonist Bayer27-9955) in the treatment of patients with type 2 diabetes mellitus inadequately controlled diet. Two or more Centers will be utilized. The overall design of the study consists of the following: A Two-Week screening period, A 21-Day Treatments Period, A 21-Day Wash-Out period, and then a crossover to the alternative treatment for 14 Days. Treatments will be administered in random order.